Defoamer and methods of use thereof

ABSTRACT

Disclosed are methods and compositions for defoaming alcoholic fermentations. An aqueous composition of polydimethylsiloxane, an ethylene oxide/propylene oxide block copolymer and a silicone/silica blend is employed to treat the fermentation for foaming.

FIELD OF THE INVENTION

The present invention pertains to an improved water-based defoamercomposition. The present invention more particularly relates to animproved water-based defoamer composition that has utility in thealcoholic fermentation of sugar cane juice and corn syrup.

BACKGROUND OF THE INVENTION

Antifoaming compositions are materials used in the prevention, removaland control of unwanted foam. Unwanted fluid foams are made up ofnumerous tiny bubbles of a mechanical or chemical origin which aregenerated within a liquid and which rise and accumulate at the liquidsurface faster than they decay.

The fields in which unwanted foams are encountered are diverse. Foamproblems can be found in polymerization, paint process, papermakingprocesses, oil drilling and refining operations, food preparation andtextile dyeing operations. Liquid coolants, hydraulic fluids,lubricants, aviation fuels and gas absorption systems may foam withundesirable results under conditions of operation. If not properlycontrolled, foam can reduce equipment capacity and increase processingtime and expense, and in some instances, cause other dangers.

Although foam can be controlled in some instances by making changes tothe process itself, or by using mechanical defoaming equipment, chemicalantifoam formulations have proven effective and economical.

Distilleries which use molasses or sugar cane juice as raw materials forethanol production face several operational problems. One of the moreserious problems is foam generation during this fermentative process.

To allow sucrose fermentation, it is necessary to decompose it tofructose and glucose, which are simpler sugars, according to thereaction:

    C.sub.12 H.sub.22 O.sub.11 +H.sub.2 O→2C.sub.2 H.sub.5 OH+2CO.sub.2 +56KCal

The components of the mixture under fermentation, composed mainly ofsugars, electrolytes, proteins and acids, get concentrated in theair-liquid interface, generating an elastic foam.

The gases that are produced during the fermentation process, due totheir lower density relative to the liquid phase, rise to the surfaceand stretch the elastic film. As this film is relatively resistant tobeing broken, the gases remain in the top part of the liquid causingbubbles (i.e. foam) to form.

This formed foam must be rigorously controlled to avoid fermentationtank overflow, which could result in loss of broth, yeasts or ethanol.

The present inventors have discovered a water-based defoamingcomposition which has proven more effective than the synthetic wax andmineral oil based defoamers typically used in the fermentation industry.

SUMMARY OF THE INVENTION

The present invention provides for defoamer compositions having utilityin alcoholic fermentations. The defoamer compositions are aqueous basedand comprise polydimethylsiloxane oils, ethylene oxide/propylene oxideblock copolymers and a silicone/silica blend.

DESCRIPTION OF THE RELATED ART

Polydimethylsiloxanes have been employed in non-aqueous mediums such asresidual petroleum stocks and crude oils as defoamers as taught in U.S.Pat. Nos. 3,700,587 and 4,082,690. Liquid organo-silicon condensationproducts or polymers in combination with silane have been taught in U.S.Pat. No. 2,702,793 as defoamers in oils and antifreezes.Polyvinylalkoxysilanes and polyvinylalkylalkoxysilanes are taught inU.S. Pat. No. 2,862,885 to control foaming in petroleum-type oils,particularly those in the lubricating oil viscosity range.

U.S. Pat. No. 3,959,175 teaches an aqueous defoamer compositioncontaining liquid polybutene. The defoamer composition can furthercomprise in part hydrophobic silica and silicone oils. U.S. Pat. No.5,288,789 teaches the use of a condensate of alkylphenol and aldehydethat has been polyoxyalkylated to reduce foam in a fermentation broth.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for compositions and methods fordefoaming alcoholic fermentations comprising a polydimethylsiloxane oil,an ethylene oxide/propylene oxide block copolymer and a silicone/silicablend in an aqueous solution. The methods comprise adding an effectivedefoaming amount of this composition to the alcoholic fermentationitself.

The polydimethylsiloxane oil is preferably selected from those having aviscosity average between about 300 and about 500 cSt (25° C.) and anaverage molecular weight (MW_(avg)) between about 20,000 and about40,000 with a molecular weight of about 28,000 to about 30,000preferred. These chemicals are available under the BAYSILONE OEL M andRHODORSYL tradenames from Bayer Corp. and Rhone Poulenc, respectively.

The ethylene oxide/propylene oxide (EO/PO) block copolymer preferablyhas a Brookfield RVT viscosity average between about 100 and about 600mPa S and a Cloud Point average between about 20 and 50 C. Thesecompounds are available commercially from Dow Chemical under the FluentCane trademark.

The silicone/silica blend is preferably comprised of methylated silicaand a dimethylsiloxane/silica reaction product in a weight ratio of 3.0%methylated silica to 27.0% dimethylsiloxane/silica reaction product andhas a Brookfield RVT viscosity average between 1000 and 30,000 cps.These compounds are commercially available from Dow Corning as DowCorning A and Dow Corning 3472, respectively.

For purposes of the present invention, the silicone/silica blend may bedefined as a blend of a siloxane compound with a silica compound.

The composition may be prepared as an aqueous solution with the weightratios of polydimethylsiloxane to EO/PO block copolymer to hydrophilicsilica ranging from about 8:10:10. Preferably the weight ratio is 4:5:5.

Additional ingredients may also be added to the aqueous composition tostabilize the composition and improve the ability of the composition todisperse over the entire foam surface. Examples of these chemicalsinclude, but are not limited to, polyether modified polysiloxane,xanthan gum, ethoxylated castor oil, glycerol monostearate, alcohol,sodium carbonate and glutaraldehyde. The key requirement being that theadditional ingredients do not affect the yeasts thereby damaging thefermentation process.

The aqueous composition can be added to the fermentation process to betreated by an conventional means. For purposes of the present invention,the phrase "an effective defoaming amount" is defined as that amount ofinventive composition which will control already formed foam.

This amount will vary based upon different parameters such as sugarjuice composition, yeasts activity, temperature, feed velocity of thesugar juice/yeast blend from the fermentation tanks, etc. Preferably,this amount ranges from about 0.3 to about 1.0 gram per liter ofproduced ethanol.

For purposes of the present invention, the phrase "alcoholicfermentations" is meant to include sugar cane juice fermentation andcorn syrup fermentation.

In order to more clearly illustrate this invention, the data set forthbelow were developed. The following examples are included as beingillustrations of the invention and should not be construed as limitingthe scope thereof.

EXAMPLES

To test the efficacy of the inventive composition as an antifoam, astandard foam knockdown test was employed. The general conditions of thetest were as follows:

    ______________________________________                                        Temperature         35° C.                                             Total Time          10 minutes                                                Air Flow            2.0 L/Min                                                 Sugar Juice/Yeasts Solution Ratio                                                                 210 mL/140 mL                                             Brix of the Juice   19                                                        Product Feed Ratio  0.2 mL/L or 0.1 mL/L of                                                       juice and yeasts                                          ______________________________________                                    

An air flowmeter was connected to a glass graduated column and set tothe indicated flow ratio. A yeast in water solution was prepared as 1part yeast per 2 parts water. The pH of the resulting solution wasadjusted to 2.3 with H₂ SO₄ (50%).

The juice and the aqueous yeast solution were then mixed in a 600 mLbeaker in the indicated ratio. This mixture was then heated to thedefined temperature. The heated mixture was then transferred to thegraduated column under the air injection.

When the foam level reached 25 cm inside the column, the antifoam wasadded at the defined feed ratio by using a 1.0 mL plastic syringe whilethe timer was simultaneously turned on. The knock down effect of theproduct and the foam level were then recorded for the indicated times.

The results of this testing are presented in Table I.

The standard was composed of 3.0% ethylene bis stearamide, 80.0% of amineral oil having 20% naphthenic carbons content, 15.0 to 20.0%aromatic carbons content and 62.0% paraffinic carbons content; and 15.0%EO/PO block copolymer. The remaining 2.0% are chemicals to stabilize andimprove product application. These are the same as those listed in theInventive Treatment A described below.

    ______________________________________                                        Inventive Treatment A Components                                                                     % (by weight)                                          ______________________________________                                        Polydimethylsiloxane Oil 500 CST                                                                     1.75                                                   (Baysilone OEL M 500/Rhodorsyl 47 V 500)                                      Polydimethylsiloxane Oil 12500 CST                                                                   2.25                                                   (Baysilone OEL M 12500/Rhodorsyl 47 V 12500)                                  Polydimethylsiloxane Oil 30000 CST                                                                   4.00                                                   (Baysilone OEL M 30000/Rhodorsyl 47 V 30000)                                  EO/PO Copolymer (Fluent Cane 152)                                                                    5.20                                                   EO/PO Copolymer (Fluent Cane 120)                                                                    8.00                                                   Silical hydrophobic silicone dioxide amorphous                                                       0.80                                                   (Rhodorsyl R 972)                                                             Stabilizers/Final Product/Improvers                                           Polyether modified polysiloxane (Tegopren 5863)                                                      1.00                                                   Xanthan Gum (Polysaccharide)                                                                         0.10                                                   Ethoxylated Castor Oil (40 EO) (Surfon R 400)                                                        2.00                                                   Glycerol Monostearate  0.50                                                   Synthetic Alcohol (20 C) (Alfol 20 plus)                                                             2.00                                                   Water                  72.19                                                  Sodium Carbonate       0.01                                                   Glutaraldehyde         0.20                                                   ______________________________________                                    

                  TABLE I                                                         ______________________________________                                        FOAM HEIGHT (cm)                                                                       Standard  Treatment A                                                                             Standard                                                                              Treatment A                                       (0.02%    (0.02%    (0.01%  (0.01%                                   TIME     active)   active)   active) active)                                  ______________________________________                                        SECONDS                                                                        0       25        25        25      25                                        5       24        18        23      20                                       10       15        15        18      17                                       15       10        13        15      16                                       20       9         9         10      14                                       25       9         7         10      12                                       30       9         7         10      10                                       35       9         7         10      10                                       40       9         7         10       9                                       45       9         7         10       9                                       50       9         7         10       9                                       55       9         7         10       9                                       60       9         7         10       9                                       MINUTES                                                                        2       12        7         12      10                                        3       13        8         16      11                                        4       14        8         17      12                                        5       15        9         17      12                                        6       15        9         18      13                                        8       15        10        19      14                                       10       15        12        19      15                                       15       15        14        19      17                                       ______________________________________                                    

As demonstrated in Table I, the inventive treatment proved moreeffective as a defoamer in a sugar fermentation than the standardproduct which is currently at use in the fermentation field. This provedtrue at both 002% and 0.01% actives.

Further testing was performed with a different inventive treatment, B,which has the following formulation:

    ______________________________________                                        Inventive Treatment B Components                                                                     % (By Weight)                                          ______________________________________                                        Polydimethylsiloxane oil 500 cst                                                                     4.00                                                   (Baysilone Oil M 500/Rhodorsyl 47 V 500                                       Silicone Compound      3.50                                                   (Dow Corning A)                                                               Base DC 3472           6.50                                                   (Dow Corning 3472)                                                            EO/PO copolymer        5.00                                                   (Fluent Cane 152)                                                             EO/PO copolymer        5.50                                                   (Fluent Cane 120)                                                             Stabilizers/Final Product Improvers                                           Xanthan gum (polysaccharide)                                                                         0.15                                                   Ethoxylated caster oil (40 EO)                                                                       2.00                                                   (Surfon R 400)                                                                Glycerol monostearate  0.65                                                   Synthetic alcohol (20 C)                                                                             2.00                                                   (Alfol 20 Plus)                                                               Water                  70.49                                                  Sodium carbonate       0.01                                                   Glutaraldehyde         0.20                                                   ______________________________________                                    

These components were blended in a stainless steel vessel with a steamjacket or coil and a stirrer with constant speed mechanism.

To test the efficacy of the inventive composition as an antifoam, astandard foam knockdown test was employed. The testing conditions were5.0 hours total fermentation time at a temperature of 35° C. The sugarjuice/yeasts solution ratio was 36 L/24 L and the brix of the juice was19. The product feed ratio was 0.02 ml/l of a mixture of sugarjuice/yeasts solution.

The yeasts solution was added to an 80 L fermentation tank graduatedfrom 10 to 10 liters. The sugar juice was added to the fermentation tankunder a feed ratio of 200 ml/minute. The time of initial fermentation isrecorded as the initial time. The sugar juice feed ratio is keptconstant and the height of the mixture of sugar juice/yeastssolution/formed foam was observed.

When the foam reached the 70 L mark inside the fermentation tank, 1.0 mlof antifoam was fed with a syringe. Every time the foam reached the 70 Llevel, 1.0 ml of antifoam was fed until the end of the fermentationprocess. The standard product was synthetic wax and mineral oil based.The results of this testing are presented in Table II.

                  TABLE II                                                        ______________________________________                                        Fermentation   Volume of Product (ml)                                         Time                      Inventive Treatment B                               (Minutes)      Standard (Neat)                                                                          (Neat)                                              ______________________________________                                         0             0.0        0.0                                                 150            1.0        1.0                                                 155            1.0        --                                                  160            1.0        --                                                  165            1.0        --                                                  170            1.0        --                                                  185            1.0        --                                                  200            1.0        --                                                  210            1.0        --                                                  225            1.0        --                                                  240            1.0        --                                                  300 (End of Fermentation)                                                                    1.0        --                                                  Total Volume of Addition                                                                     10.0       1.0                                                 ______________________________________                                    

The results of this testing demonstrate that the inventive compositionwas more effective than the traditional treatment at inhibiting foamformation in an alcoholic fermentation process.

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

Having thus described the invention, what we claim is:
 1. A method fordefoaming an alcoholic fermentation comprising adding to saidfermentation an effective defoaming amount of an aqueous compositioncomprising (A) a polydimethylsiloxane oil, (B) an ethyleneoxide/propylene oxide block copolymer, and (C) a silicone/silica blend.2. The method as claimed in claim 1 wherein said polydimethylsiloxaneoil has an average viscosity of about 300 to about 500 cSt at 25° C. 3.The method as claimed in claim 2 wherein said polydimethylsiloxane oilhas an average molecular weight of about 20,000 to about 40,000.
 4. Themethod as claimed in claim 1 wherein said ethylene oxide/propylene oxideblock copolymer has a Brookfield RVT viscosity average between about 100and about 600 mPa S and a Cloud Point average between about 20 and 50°C.
 5. The method as claimed in claim 1 wherein said silicone/silicablend comprises a dimethylsiloxane-silica reaction product/methylatedsilica.
 6. The method as claimed in claim 1 wherein the weight ratio of(A):(B):(C) is from about 8:10:10 to about 4:5:5.
 7. The method asclaimed in claim 1 wherein said composition further comprises aningredient selected from the group consisting of polyether modifiedpolysiloxane, xanthan gum, ethoxylated castor oil, glycerolmonostearate, alcohol, sodium carbonate and glutaraldehyde.
 8. Themethod as claimed in claim 1 wherein said alcoholic fermentationcontains yeast.
 9. The method as claimed in claim 1 wherein saidalcoholic fermentation is selected from the group consisting of sugarcane juice fermentation and corn syrup fermentation.
 10. The method asclaimed in claim 1 wherein said composition is added to saidfermentation in an amount ranging from about 0.3 to about 1.0 gram perliter of ethanol produced.